CONTENTS -- INTRODUCTION -- CHAPTER 1: ZG AS A MULTIPLE PULLBACK -- CHAPTER 2: MODULES OVER PULLBACKS -- CHAPTER 3: MODULES OVER THE COORDINATE RINGS -- CHAPTER 4: REDUCTION TO A MATRIX PROBLEM -- CHAPTER 5: LOCALIZATIONS AND COMPLETIONS -- CHAPTER 6: SOLUTION OF THE MATRIX PROBLEM -- CHAPTER 7: INDECOMPOSABLE ARTINIAN ZG-MODULES -- CHAPTER 8: INDECOMPOSABLE NON-ARTINIAN ZG-MODULES -- CHAPTER 9: DIRECT SUM BEHAVIOR -- CHAPTER 10: LOCALLY QUASI-FREE CLASS GROUPS -- CHAPTER 11: APPLICATIONS -- REFERENCES